Sash locks for casement and awning windows are well known. Casement and awning windows are generally defined as having a glass panel, with each panel in a sash, with the sash moveable within a frame which is secured in the dwelling in which the window resides. The sash is mounted in a window frame, defined by jamb liners on the sides, a head jamb on the top and a sill on the bottom. Typically, the sash is secured to the frame and is hinged to the frame through a window operator having hinges.
Typically, for large casement and awning style windows, a single point sash lock is insufficient to adequately secure the full length of the sash in place. If a single point sash lock is used for casement windows which are typically larger than two to three feet as measured on one side, the corners of the sash may not be tightly secured in the frame of the window. Thus, the two point lock system is desirable for larger windows.
U.S. Pat. No. 4,095,829 discloses a two point lock system for locking windows. Among other things, the patent is directed to a lost motion mechanism which results in one engaging cam rotating earlier than a second engaging cam. This lost motion is achieved by a pin and slot configuration whereby a pin moves through a slot, but does not move the cam initially.
U.S. Pat. No. 5,087,087 discloses a casement sash lock. This patent is directed to a catch operator being secured in a housing, such that it is not extending outward in an exposed position.
U.S. Pat. No. 4,610,472 discloses a casement window securing mechanism which utilizes a double cam system whereby rotation of the second cam occurs in response to rotation of the first cam. The second cam draws a catch at a rate varying with the cam angle of rotation. U.S. Pat. No. 4,253,688 discloses yet another type of sash lock.
The prior designs for sash locks suffer from a number of drawbacks. One drawback is often times the cam engagement mechanisms are complex, involving moving parts, and do not adequately center the sash within the frame and enclosed position.
Another problem associated with prior sash locks are the connecting bar between the engaging cams was pushed rather than pulled when closing the sash. The pushing action results in flexing of the connecting rod, which creates an inefficient mechanism for moving the connected cam to lock the sash in place.